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FERMILAB-PROPOSAL 0913A Proposal for Calibration and Testing of a Transition Radiation Detectorfor Space ApplicationsSimon P. SwordyEnrico Fermi Institute, University of Chicago, Chicago IL 60637, U.S.A.AbstractWe plan to use transition radiation detectors (TRD) for the measurement of theLorentz factor (y) of high energy cosmic ray nuclei on spacecraft and high altitudeballoons. These are designed to provide response over a range of particle energiesfrom y -500 to y -10000. Since the absolute response of a TRD is difficult to accu-rately predict from calculation the calibration of a test unit with particles of knowny is essential to verify performance. We propose to use a suitably instrumentedcalibration beam at FNAL for this purpose. With auxilary detectors we plan toidentify p,/i,lr, and e in the beam and use this tagging to determine the response ofthe TRD for particles of different y. For a beam with particle momenta somewherein the range 100-500GV we expect to collect an adequate number of data points fora calibration. Although it is desirable to collect as many data points as possible aminimum test would consist of determining the response for a low y value (likelyfrom p) and for a high y (from e). Even this small amount of information would beuseful to test the calculated response.1 IntroductionThe variation of the elemental abundances of cosmic ray nuclei as a functionof energy has long been viewed to be a crucial measurement for the originsof cosmic rays. While much progress has been made in this area, elementalcomposition measurements at energies above ~100GeV exist only for the moreabundant species and disappear altogether above 100TeV. Although manycosmic rays have been measured at these and higher energies, the elementalcomposition is not known. The TRDs discussed in this proposal are designedto fly on NASA missions to investigate the elemental composition at highenergies by a determination of y for high energy cosmic ray nuclei. They useplastic fiber TR radiators and detectors filled with xenon gas. A novel aspect ofthis TRD is the use of thin proportional tube detectors which can be operatedin external vacuum. Previous TRD systems flown in space have used multiwireproportional chambers as detectors. Since no pressure shell is required for thenew design there are significant savings in weight and complexity for this newtype of TRD in space.